Enhancing biofloc system performance using yeast-fermented water hyacinth (Pontederia crassipes Mart.): impacts on water quality, floc dynamics, and microbial abundance in tilapia culture

Biofloc technology (BFT) is an eco-friendly aquaculture method that utilizes the recycling of nutrients by microorganisms, thereby improving the water quality and offering additional nutrition. In this study, different parts (stem, leaf, and mixtures) of water hyacinth, Pontederia crassipes, were tested, both yeast fermented and unfermented, as alternative carbon sources in BFT systems for the rearing of genetically improved farmed tilapia. The 90-day experiment involved seven treatments, six biofloc systems, and a clear-water control (7*3 completely randomized design), to evaluate water quality dynamics, floc characteristics, and bacterial load. Yeast-incorporated treatments, especially those using stem-derived or mixed carbon, showed more stability in pH and alkalinity profiles and significantly enhanced nitrogen cycling efficiency. These systems showed lower total ammonia nitrogen and nitrite levels compared to the control (p < 0.05) reflecting robust nitrification. Floc analysis revealed that yeast fermentation produced larger, denser, and more stable bioflocs, resulting in the formation of compact, porous bioflocs enriched with diverse microbial communities. These findings indicate that integrating yeast fermentation with locally available macrophyte, P. crassipes can enhance biofloc quality and microbial activity and promote effective water quality management in intensive aquaculture practices. Such integrative approaches offer promising pathways toward sustainable, cost-effective, and ecologically sound aquaculture practices, particularly in resource-limited or tropical regions.